Orthognathic biomechanical simulation

ABSTRACT

Disclosed is a method of simulating mastication. The method includes obtaining computer-readable three-dimensional representations of a first skeletal fragment including a portion of at least one of a mandible and a maxilla and of a recipient skeletal fragment including a portion of at least one of a mandible and a maxilla. The method also includes obtaining placement data and obtaining muscle insertion data. The method also includes simulating a contraction of a muscle positioned according to the muscle insertion data in a representation of a surgical hybrid comprising at least a portion of the first skeletal fragment positioned according to the placement data relative to at least a portion of the recipient skeletal fragment. The method also includes outputting a representation of mastication represented by the simulating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/910,204, filed Nov. 29, 2013; 61/940,196, filedFeb. 14, 2014; and 62/049,866, filed Sep. 12, 2014, each of which ishereby incorporated by reference in its entirety.

GOVERNMENT SUPPORT STATEMENT

This invention was made with government support under NCATS Grant No.UL1TR000424-06 awarded by the National Institutes of Health. Thegovernment has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to the field of surgery, particularlycraniomaxillofacial surgery, and specifically to the field ofcomputer-assisted craniomaxillofacial surgery and all relatedorthognathic, neurosurgical and head/face/neck surgical procedures andassociated methods, tools, and systems.

BACKGROUND OF THE INVENTION

Facial transplantation represents one of the most complicated scenariosin craniomaxillofacial surgery due to skeletal, aesthetic, and dentaldiscrepancies between donor and recipient. Use of computer technology toimprove accuracy and precision of craniomaxillofacial surgicalprocedures has been described for nearly 30 years, since the increasingavailability of computed topography (CT) prompted the development of aCT-based surgical simulation plan for osteotomies.

Two broad approaches to computer-assisted surgery (CAS) have gainedpopularity: 1) pre-operative computer surgical planning and the use ofthree-dimensional computer manufactured surgical guides (3D CAD/CAM) tocut and reposition bone and soft tissue, and 2) utilizing intraoperativefeedback relative to preoperative imaging for the surgeon to providemore objective data on what is happening beyond the “eyeball test.”However, none are meant for real-time placement feedback in areas whereguide placement is more challenging, such as the three-dimensionalfacial skeleton. Also, there are no single platforms built to provideBOTH planning AND navigation—with seamless integration. Additionally,standard off-the-shelf vendor computer-assisted surgery systems may notprovide custom features to mitigate problems associated with theincreased complexity of this particular procedure. Furthermore, thereare currently no validated methods for optimizing outcomes related tofacial (e.g., soft tissue), skeletal (e.g., hard tissue), and occlusal(e.g., dental) inconsistencies and for predicting post-operativefunction (e.g., mastication) in the setting of a donor-to-recipientanthropometric mismatch—a major hurdle to achieving this specialty'sfull potential.

One known system includes pre-operative planning and cutting guides byway of computer manufactured stereolithographic models for human facialtransplantation. However, such a system uses standard off-the-shelfvendor systems and does not include necessary features to mitigate theincreased complexity of this particular procedure.

Additionally, known CAS paradigms for craniomaxillofacial surgeryprovide little capacity for intraoperative plan updates. This featurebecomes especially important since, in some circumstances during thetransplantation surgery, it may be necessary to revise and update thepreoperative plans intraoperatively.

What is needed in the art, therefore, is a single, fully-integratedplatform, providing a computer-assisted surgery solution customized forpre-operative planning, intraoperative navigation, and dynamic,instantaneous feedback, for example, in the form of biomechanicalsimulation and real-time cephalometrics, for post-operative functionprediction in facial transplantation that addresses common shortcomingsof existing CAS systems and has the potential to improve outcomes acrossboth the pediatric and adult-based patient population.

SUMMARY

According to some embodiments, a method of simulating mastication isdisclosed. The method includes obtaining a computer-readablethree-dimensional representation of a first skeletal fragment comprisinga portion of at least one of a mandible and a maxilla, obtaining acomputer readable three-dimensional representation of a recipientskeletal fragment comprising a portion of at least one of a mandible anda maxilla, obtaining placement data representing a position of at leasta portion of the first skeletal fragment relative to at least a portionof the recipient skeletal fragment, obtaining muscle insertion datarepresenting at least one muscle insertion location on at least one ofthe first skeletal fragment and the recipient skeletal fragment,simulating a contraction of a muscle positioned according to the muscleinsertion data in a representation of a surgical hybrid comprising atleast a portion of the first skeletal fragment positioned according tothe placement data relative to at least a portion of the recipientskeletal fragment, and outputting a representation of masticationrepresented by the simulating.

Various optional features of the above embodiments include thefollowing. The obtaining placement data may include obtaining placementdata prior to a surgery to transplant at least a portion of the firstskeletal fragment into a recipient. The obtaining placement data mayinclude obtaining placement data during a surgery to transplant at leasta portion of the first skeletal fragment into a recipient. The obtainingplacement data may include tracking a position of at least a portion ofthe first skeletal fragment during the surgery. The method may includeobtaining muscle activation data representing at least one musclecontraction, where the simulating includes simulating a contraction of amuscle according to the muscle activation data.

According to some embodiments, a method of simulating mastication isdisclosed. The method includes obtaining a computer-readablethree-dimensional representation of an osseointegrative implantcomprising a portion of at least one of a mandible and a maxilla,obtaining a computer readable three-dimensional representation of arecipient skeletal fragment comprising a portion of at least one of amandible and a maxilla, obtaining placement data representing a positionof at least a portion of the osseointegrative implant relative to atleast a portion of the recipient skeletal fragment, obtaining muscleinsertion data representing at least one muscle insertion location on atleast one of the osseointegrative implant and the recipient skeletalfragment, simulating a contraction of a muscle positioned according tothe muscle insertion data in a representation of a surgical hybridcomprising at least a portion of the osseointegrative implant positionedaccording to the placement data relative to at least a portion of therecipient skeletal fragment, and outputting a representation ofmastication represented by the simulating.

Various optional features of the above embodiments include thefollowing. The obtaining placement data may include obtaining placementdata prior to a surgery to implant at least a portion of theosseointegrative implant into a recipient. The obtaining placement datamay include obtaining placement data during a surgery to implant atleast a portion of the osseointegrative implant into a recipient. Theobtaining placement data may include tracking a position of at least aportion of the osseointegrative implant during the surgery. The methodmay also include obtaining muscle activation data representing at leastone muscle contraction, wherein the simulating includes simulating acontraction of a muscle according to the muscle activation data.

According to some embodiments, a system for simulating mastication isdisclosed. The system includes at least one electronic memory and atleast one electronic processor, the at least one electronic memoryincluding instructions which, when executed by the at least oneelectronic processor, cause the at least one electronic processor toperform a method including: obtaining a computer-readablethree-dimensional representation of a first skeletal fragment comprisinga portion of at least one of a mandible and a maxilla, obtaining acomputer readable three-dimensional representation of a recipientskeletal fragment comprising a portion of at least one of a mandible anda maxilla, obtaining placement data representing a position of at leasta portion of the first skeletal fragment relative to at least a portionof the recipient skeletal fragment, obtaining muscle insertion datarepresenting at least one muscle insertion location on at least one ofthe first skeletal fragment and the recipient skeletal fragment,simulating a contraction of a muscle positioned according to the muscleinsertion data in a representation of a surgical hybrid comprising atleast a portion of the first skeletal fragment positioned according tothe placement data relative to at least a portion of the recipientskeletal fragment, and outputting a representation of masticationrepresented by the simulating.

Various optional features of the above embodiments include thefollowing. The obtaining placement data may include obtaining placementdata prior to a surgery to transplant at least a portion of the firstskeletal fragment into a recipient. the obtaining placement data mayinclude obtaining placement data during a surgery to transplant at leasta portion of the first skeletal fragment into a recipient. The obtainingplacement data may include tracking a position of at least a portion ofthe first skeletal fragment during the surgery. The at least oneelectronic memory may further include instructions which, when executedby the at least one electronic processor, further cause the at least oneelectronic processor to obtain muscle activation data representing atleast one muscle contraction, where the simulating includes simulating acontraction of a muscle according to the muscle activation data.

According to some embodiments, a system for simulating mastication isdisclosed. The system includes at least one electronic memory and atleast one electronic processor, the at least one electronic memoryincluding instructions which, when executed by the at least oneelectronic processor, cause the at least one electronic processor toperform a method including: obtaining a computer-readablethree-dimensional representation of an osseointegrative implantcomprising a portion of at least one of a mandible and a maxilla,obtaining a computer readable three-dimensional representation of arecipient skeletal fragment comprising a portion of at least one of amandible and a maxilla, obtaining placement data representing a positionof at least a portion of the osseointegrative implant relative to atleast a portion of the recipient skeletal fragment, obtaining muscleinsertion data representing at least one muscle insertion location on atleast one of the osseointegrative implant and the recipient skeletalfragment, simulating a contraction of a muscle positioned according tothe muscle insertion data in a representation of a surgical hybridcomprising at least a portion of the osseointegrative implant positionedaccording to the placement data relative to at least a portion of therecipient skeletal fragment, and outputting a representation ofmastication represented by the simulating.

Various optional features of the above embodiments include thefollowing. The obtaining placement data may include obtaining placementdata prior to a surgery to implant at least a portion of theosseointegrative implant into a recipient. The obtaining placement datamay include obtaining placement data during a surgery to implant atleast a portion of the osseointegrative implant into a recipient. Theobtaining placement data may include tracking a position of at least aportion of the osseointegrative implant during the surgery. The at leastone electronic memory may further include instructions which, whenexecuted by the at least one electronic processor, further cause the atleast one electronic processor to obtain muscle activation datarepresenting at least one muscle contraction, wherein the simulatingincludes simulating a contraction of a muscle according to the muscleactivation data.

Additional advantages of the embodiments will be set forth in part inthe description which follows, and in part will be understood from thedescription, or may be learned by practice of the invention. Theadvantages will be realized and attained by means of the elements andcombinations particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a surgical system and method that closes theloop between surgical planning, navigation, and enabling intraoperativeupdates to a surgical plan.

FIGS. 2A-2C provide a schematic overview of a surgical system.

FIGS. 2D-2G are graphical representations of some components and/orfeatures of the surgical system of FIGS. 2A-2C.

FIG. 3 is a flow chart depicting a procedure associated with use of thesurgical system, for example, the surgical system of FIGS. 2A-2C.

FIG. 4A is a CT-scan of reconstructed images of a size-mismatched facialskeleton generated from segmentation software utilized for pre-operativeplanning.

FIG. 4B shows a segmented arterial system of a craniomaxillofacialskeleton generated from CT angiography (CTA) data allowing 3D,intraoperative mapping.

FIGS. 5A-5B show depictions of on-screen images provided by a surgicalsystem, such as the surgical system of FIG. 2A displaying real-time,dynamic cephalometrics and pertinent measurements applicable to humans.FIG. 5A shows a donor's face-jaw-teeth alloflap in suboptimal positionas compared to a recipient's cranium. FIG. 5B shows appropriateface-jaw-teeth positioning with immediate surgeon feedback and updatedcephalometric data pertinent to a pre-clinical investigation. A surgeonmay adjust the position of face-jaw-teeth segment upwards, downwards,forwards, or backwards based on this real-time cephalometric feedback,as this information helps to predict optimal form and function. Forinstance, placing the face-jaw-teeth segment forward may improve thepatient's airway, but if moved too far forward, it may cause the patientto have a significant overjet (i.e. malocclusion) and abnormalappearance in a profile view.

FIG. 6 shows some pre-bent fixation plates with screw holes designedvirtually to accommodate the donor-to-recipient skeletal mismatch areasand matching navigational cutting guides of a surgical system, forexample, the surgical system of FIGS. 2A-2C.

FIG. 7A shows a kinematic reference mount of an embodiment as it isaffixed onto a donor's cranium with intermaxillary screws. A permanentsuture (not visible) attaches stabilizers, such as springs and/or crossbars, which allow easy removal and replacement during surgery.

FIG. 7B shows a detachable rigid body with reflective markers attachedto the reference body.

FIGS. 8A-8C are illustrations of cutting guides of the embodiments withnavigational capabilities. FIG. 8A illustrates a donor face-jaw-teethalloflap recovery, FIG. 8B shows a recipient preparation prior totransplant, and FIG. 8C illustrates a custom pre-bent fixation plate andpalatal splint designed to achieve face-jaw-teeth alignment and skeletalinset.

FIGS. 9A-9D are renderings showing exemplary surgical results.

FIGS. 10A-10C are a top-view (bird's eye view), a left-sided profileview, and a frontal view, respectively, of images displayed by animaging system of a surgical system. The images depict a recipientskeleton and include real-time assessment of planned versus actualface-jaw-teeth positions.

FIGS. 11A-11B are “on screen” images displayed by an imaging sub-systemof a surgical system. The images depict an ideal location of a cuttingguide versus an actual position and an actual inset position of a donoralloflap for aesthetic, dental, and skeletal relation in size-mismatcheddonors due to anterior translation of cutting guide.

FIG. 12 illustrates a virtual osteotomy and planned cut plane placementon virtual representations of a skeletal feature.

FIGS. 13A-13D illustrate a virtual placement of a cutting guidealongside (FIGS. 13A-13B) and illustrated representations of an actualplacement (FIGS. 13C-13D).

FIG. 14A illustrates a perspective view of a variation of a cuttingguide, for example, a variation of the cutting guide of FIG. 13.

FIG. 14B illustrates a top view of a variation of a cutting guide, forexample, a variation of the cutting guide of FIG. 13.

FIGS. 15A and 15B illustrate a biomechanical simulation of masticationof a recipient skull according to some embodiments.

FIGS. 16A and 16B illustrate a biomechanical simulation of masticationof a hybrid skull according to some embodiments.

FIG. 17 is a workflow of a method according to various embodiments.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments,examples of which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein. For example, a range of “less than 10” can include any and allsub-ranges between (and including) the minimum value of zero and themaximum value of 10, that is, any and all sub-ranges having a minimumvalue of equal to or greater than zero and a maximum value of equal toor less than 10, e.g., 1 to 5. In certain cases, the numerical values asstated for the parameter can take on negative values. In this case, theexample value of range stated as “less that 10” can assume negativevalues, e.g. −1, −2, −3, −10, −20, −30, etc.

The following embodiments are described for illustrative purposes onlywith reference to the figures. Those of skill in the art will appreciatethat the following description is exemplary in nature, and that variousmodifications to the parameters set forth herein could be made withoutdeparting from the scope of the present invention. It is intended thatthe specification and examples be considered as examples only. Thevarious embodiments are not necessarily mutually exclusive, as someembodiments can be combined with one or more other embodiments to formnew embodiments.

Disclosed are embodiments of a computer-assisted surgery system thatprovides for large animal and human pre-operative planning,intraoperative navigation which includes trackable surgical cuttingguides, and dynamic, real-time instantaneous feedback of biomechanicalsimulation and cephalometric measurements/angles as needed for medicalprocedures, such as facial transplantation, and many other instances ofcraniomaxillofacial and orthognathic surgery. Such a system can bereferred to as a computer-assisted planning and execution (C.A.P.E.)system and can be exploited in complex craniomaxillofacial surgery likeLe Fort-based, face-jaw-teeth transplantation, for example, and any typeof orthognathic surgical procedure affecting one's dental alignment, andcan include cross-gender facial transplantation.

The fundamental paradigm for computer-assisted surgery (CAS) involvesdeveloping a surgical plan, registering the plan and instruments withrespect to the patient, and carrying out the procedure according to theplan. Embodiments described herein include features for workstationmodules within a CAS paradigm. As shown in FIG. 1, a surgical system ofthe embodiments can enable intraoperative evaluation of a surgical planand can provide instrumentation for intraoperative planupdates/revisions when needed.

Embodiments can include a system with integrated planning and navigationmodules, for example, a system for tracking donor and recipient surgicalprocedures simultaneously. In general, features of such a system caninclude: 1) two or more networked workstations concurrently used inplanning and navigation of the two simultaneous surgeries for both donorand recipient irrespective of geographic proximity, 2) two or moretrackers, such as electromagnetic trackers, optical trackers (e.g.,Polaris, NDI Inc.), and the like, for tracking bone fragments, tools,and soft tissues, 3) one or more guides, reference kinematic markers,etc. as required for navigation. These features are described in furtherdetail with respect to FIGS. 2A-2G.

Preoperative planning can include the following tasks: a) segmentationand volumetric reconstruction of the donor and recipient facial anatomy;b) planning for patient-specific cutting guide placement; c)cephalometric analysis and biomechanical simulation of the hybridskeleton's occlusion and masticatory function, respectively; d)fabrication of the hybrid cutting guides enabling both geometric(“snap-on” fit) and optical navigation; e) 3D mapping the vascularsystem on both recipient and donor facial anatomy; and f) plan updates,if necessary, based on the feedback from the intraoperative module. Asused herein, “snap-on fit” or “snap-on” or “snap on” are used todescribe the way an item, such as a cutting guide, attaches to apre-determined area. That is, the cutting guide actually “snaps-on” to acertain pre-determined area along the patient being's anatomy, such asthe facial skeleton, and in all other areas it doesn't fit properlysince size and width varies throughout significantly with manyconvexities and concavities.

Intraoperative tasks of embodiments described herein can generallyinclude: 1) registering the preoperative model reconstructed from the CTdata to donor and recipient anatomy; 2) visualizing (e.g., usinginformation from the tracker, such as an electromagnetic tracker,optical tracker, and the like) the instruments and cutting guides tohelp the surgeon navigate; 3) verifying the placement of cutting guides,and performing real-time cephalometric and biomechanical simulation forocclusion analysis, if, for any reason, the osteotomy sites need to berevised; 4) dynamically tracking the attachment of the donor fragment tothe recipient and providing quantitative and qualitative (e.g., visual)feedback to the surgeon for the purpose of improving final outcomesrelated to form (i.e., overall facial aesthetics) and function (i.e.,mastication, occlusion relation, airway patency). Such a procedure isdescribed in further detail below with respect to FIG. 3.

Preoperative Planning

In general, a method for performing a surgery includes a virtualsurgical planning step that includes performing segmentation and 3Dreconstruction of recipient and donor CT scans (e.g., Mimics 15.01,Materialise, Leuven Belgium). Virtual osteotomies can then be performedwithin the software to optimize the donor/recipient match.Patient-customized cutting guide templates can then be created (3-matic7.01, Materialize, Leuven, Belgium). These templates can then berapid-prototyped via an additive manufacturing modeling process, whichcan include, but is not limited to, stereolithography or 3D printing andthe like. The surgical method and system for performing surgery aredescribed in further detail below.

Referring to FIGS. 4A and 4B, during the initial planning stage,surgeons determine a virtual plan 401 based on the recipient'scraniomaxillofacial deformity irrespective of the donor. From registeredCT data, segmentation software generates volume data for specific keyelements (e.g., the mandible, maxilla, and cranium) used forpreoperative planning and visualization. The planning workstationautomatically generates the expected cut geometry of the donor fragment402 together with the recipient, thereby defining the predicted facialskeleton with accompanying hybrid occlusion. If available, blood vessels404 are segmented from CT angiography scans as shown in FIG. 4B. Thatis, in an embodiment, nerves (via known nerve foramens) and vessels(both arteries and veins) can be localized to provide a full anatomical“road map” to the surgeons for a more precise, time-saving anatomicaldissection with perhaps decreased blood loss and smaller incisions. Theplanning module can also perform predictive biomechanical simulation andcephalometric analysis related to face-jaw-teeth harmony on varyingconstructions of the hybrid donor and recipient jaw, such as that shownin FIGS. 5A-5B. Using this tool, the surgeon can evaluate differentplacements for the donor's face-jaw-teeth alloflap on the recipient'sfacial skeleton in relation to orbital volumes, airway patency, facialprojection, and dental alignment. An automated cephalometric computationfor the hybrid face indicates the validity of the planned surgery fromboth an aesthetic, functional and reconstructive standpoint based onvarious measurements of pertinent landmarks as shown, for example, inTables 1A-B.

TABLE 1A Pertinent landmarks for cephalometric analysis SYMBOL NAME andDEFINITION Go Gonion: a point mid-way between points defining angles ofthe mandible Gn Gnathion: most convex point located at the symphysis ofthe mandible ALV Alveolare: mid-line of alveolar process of the upperjaw, at incisor - alveolar junction LIB Lower Incisor Base: midline ofanterior border of alveolar process of mandible at the incisor-alveolarjunction PA Parietale: most superior aspect of skull in the midline,(formed by nuchal crest of occipital bone and parietal bone) PRNPronasale: bony landmark representing anterior limit of nasal bone ZYZygion: most lateral point of malar bone OCC Occipital region: midpointbetween the occipital condyles

TABLE 1B Cephalometric measurements and related units. Measure LIB- PA-PA- ALV- ZY- PA- Go- Go- PA- LIB- OCC- PA- PRN- PRN- PRN- ZY PRN Gn LIBALV ALV Overbite Overjet PRN ALV ALV LIB LIB Units mm mm mm Mm mm mm Mmmm mm deg deg deg deg

To evaluate and predict cephalometric relationships both during planningand intra-operative environments, the system can use validated,translational landmarks between swine and human to thereby alloweffective pre-clinical investigation. The cephalometric parametersdefined by these landmarks can be automatically recalculated as thesurgeon relocates the bone fragments using a workstation's graphicaluser interface.

Preoperative planning can also involve fabrication of custom guides 207(as shown in FIG. 6) and palatal splints 223 (as shown in FIG. 8C).Planned cut planes 403 (as shown in FIG. 4) can be used for defining thegeometry of the cutting guides to thereby provide patient-specificcutting guides. These cutting guides can be designed according to theskeletal features through which the cutting plane intersects, such as anouter skeletal surface of a cross section defined by the cutting plane,and can be fabricated via stereolithography, or via any additivemanufacture technology. In an embodiment, custom guide t m plates can beseparately designed and navigational registration elements can be added(Freeform Plus. 3D Systems, Rock Hill, S.C.). As discussed above, thesurgical guides can be manufactured via additive manufacturingtechnology (AMT). The cutting guides can, therefore, be a 3D printingmaterial such as a polymer, and can include an attachment surface 216configured for attaching to a skeletal feature, and can have a “snap-on”fit to both donor and recipient. As described above, the attachmentsurface may include a contoured surface that corresponds to the contoursof the skeletal feature within the planned cut planes. A navigationsurface, such as a reference geometry 217 connected, built into, orattached to the guide structure directly or via attachment guides (notshown), enables dynamic intraoperative tracking of guides with respectto the patient's skeleton. Palatal splints ensure planned dento-skeletalalignment fixation following Le Fort-type facial transplants or anysimilar type of surgery. Fixation plates 216 can include a primarysurface 216′ and a plurality of fixation surfaces 221, such as eyelets,for screw placement to provide rigid immobilization at the irregularskeletal contour areas along various donor-to-recipient interfaces.Having pre-bent fixation plates decreases total operative times andhelps to confirm accurate skeletal alignment by overcoming step-offdeformities at bone-to-bone interfaces. Accordingly, at least one of theplurality of fixation surfaces can be located on one side of the primarysurface and configured for attaching the fixation surface to a donorskeleton fragment, and at least one of another of the plurality offixation surfaces is located on another side of the primary surface andconfigured for attaching the fixation surface to a recipient skeleton.The whole fixation plate or just portions of the fixation plate, such asthe primary surface or fixation surfaces can be manufactured viaadditive manufacturing technology.

The cutting guide's navigation surface can include trackable objects,for example, on the reference geometry, such as infrared (IR) reflectivecoatings or IR emitters. For example, the trackable objects can includea plurality of integrated tracking spheres, each of which has an IRreflection surfaces.

Intraoperative Surgical Assistance

Individual navigation for both donor and recipient surgeries tracks thecutting guides with respect to planned positions. Surgeons can attach areference unit, such as a kinematic reference mount to threeintramedullary fixation (IMF) screws arranged in a triangular pattern oneach the donor and recipient craniums as shown in FIG. 7A-7B.Accordingly, in an embodiment, there is a reference unit 205 forproviding real-time surgical navigation assistance. The reference unitfor providing real-time surgical navigation assistance can include akinematic mount 203, at least one fixation rod 202, at least one support204, and reference geometry 201. The kinematic mount 203 can include abase with a plurality of recesses defined by sidewalls 233, at least onepair of slots 235 defined by portions of the sidewalls, with each slotof the pair formed across the recess from the other slot, and at leastone guide hole 237 extending through a length of the fixation plate. Theat least one fixation rod 202 can extend through the at least one guidehole 237. An end of the at least one support rod can be configured forattaching to a skeleton of a being 209. The at least one support can bedisposed in the pair of slots and can be configured to attach to thebeing. The reference geometry 201 can be attached to the at least onefixation rod.

The at least one support 204 can include at least one cross-bar 204′with ends that are configured for placement in the slots 235, and aspring 204″ attached at one end to the at least one cross-bar 204′ andattached at another end to the patient (e.g., a human-being). The springattached at another end to the being can be attached via a suture(further described below). The reference unit 205 can further include atrackable object disposed on the reference geometry. The trackableobject disposed on the reference geometry can include an IR reflectivesurface. The mount 203 can be made via additive manufacturing techniquesand can therefore include a polymer. The at least one fixation rod caninclude a plurality of intramedullary fixation screws. The base can beconfigured for being detachably mounted on the skeleton of the being209. The intramedullary fixation screws can be arranged in a triangularpattern. Accordingly the guide-holes can be configured in a triangularpattern on the base.

Accordingly, the mount design permits flexibility in the placement ofthe IMF screws so that no template is necessary. A spring 204″ canattach to each IMF screw via suture threaded through, for example, theeyelets. These springs hold the cranial mount 203 in place and alloweasy removal and replacement of the cranial mount (e.g. duringpositional changes required for bone cuts and soft tissue dissections).This may provide detachability and use of Intramaxillary fixation (IMF)screws for stable attachment

The reference geometry 201 (e.g., which can be purchased from Brainlab,Westchester, Ill., USA) attached to the kinematic mount 203 provides astatic coordinate frame attached to the patient. The surgeon candigitize three bony landmarks (e.g., the inferior aspect of the orbitsand antero-superior maxilla) to define a rough registration between theenvironment and virtual models. For example, three, consistent pointscan be selected which can be quick to find, easy to reproduce onnumerous occasions, and would remain constant irrespective of the userand his/her experience with the systems of the embodiments. The surgeoncan thereby collect several point sets from exposed bone using adigitization tool and uses an iterative closest point registrationtechnique to refine the registration. As shown in FIG. 8, onceregistered, the surgeon navigates the placement of the cutting guide 217using the combination of “snap-on” geometric design and the trackingsystem coupled to visual feedback. This allows assessment ofinaccuracies related to soft tissue interference, iatrogenicmalpositioning, and anatomical changes since acquiring original CT scandata, and/or imperfections in cutting guide design or additivemanufacturing process.

Self-drilling screws affix the cutting guide to the patient's skeletonto ensure osteotomies are performed along pre-defined planes, maximizingbony congruity. After dissecting the donor's maxillofacial fragment andpreparing the recipient's anatomy, the surgical team transfers thefacial alloflap. The system is configured to track the finalthree-dimensional placement of, for example, the Le Fort-based alloflapproviding real-time visualization such as that shown in FIG. 5A-5B. Thisprovides real-time visualization of important structures such as neworbital volumes (vertical limit of inset), airway patency (posteriorhorizontal limit of inset), and facial projection (anterior horizontallimit of inset). Once confirmed, the surgeon fixates the donor alloflapto the recipient following conventional techniques with plates andscrews.

Accordingly, returning to FIGS. 2A-2G, there is a system 200 fortracking donor and recipient surgical procedures simultaneously. Thesystem can include a donor sub-system 200-D, a recipient sub-system200-R and a communications link (indicated by the horizontaldotted-line) such as a communication link that provides TCP/IP datatransfer between the donor and recipient sub-systems. The donorsub-system can include a first computer workstation 215-D, a firstcranial reference module 205-D, a first cutting guide 207-D forattaching to a preselected location of a donor skeleton 206, a firstfragment reference module 201-D′, and a first tracker 213-D. The firstcutting guide 207-D can include an attachment surface 219-R configuredfor attaching to a skeletal feature, and a navigation surface 217-Dconnected to the attachment surface and comprising a trackable referencegeometry. The first tracker 213-D may be configured to be incommunication with the first computer workstation, for example, via acommunications link. The first tracker can be configured to track, forexample via IR optical tracking, a location of a portion of the firstcranial reference module, a portion of the first cutting guide and aportion of the first fragment reference module. The recipient sub-system200-R can include a second computer workstation 215-R, a second cranialreference module 205-R, and a second tracker 213-R. The second tracker213-R can be configured to be in communication with the second computerworkstation, for example, via a communications link. The second trackercan be configured to track, for example, via IR optical tracking, alocation of a portion of the second cranial reference module. Thecommunications link can connect the first computer workstation and thesecond computer workstation such that the first computer workstation andsecond computer workstation are able to communicate.

The recipient sub-system 200-R can further include a second fragmentreference unit 201-R. The second tracker 213-R can further be configuredto track a location of a portion of the second fragment unit.

The recipient sub-system 200-R can further include a second cuttingguide 219-R for attaching to a preselected location of a recipientskeleton 208. The second tracker 213-R can further be configured totrack a location of a portion of the second cutting guide.

Additionally, when a surgeon has removed the donor skeletal fragmentfrom the donor, it can then be transferred for attachment onto therecipient. Accordingly, the second tracker 213-R can be furtherconfigured to track a location of a portion of the first cutting guide207-D so that it can be matched relative a position of the secondcranial reference module 205-R.

The first cranial reference unit, the second cranial reference unit, orboth the first and second cranial reference units can include akinematic mount 205 as described above.

Using the system of FIGS. 2A-2G, it is possible to execute a surgicalmethod, such as the surgical method described in FIG. 3. For example, instep 302 a donor, recipient and transplant type are identified. CT/CTAscans of both the donor and recipient are collected and 3D models arecreated in step 304. The donor and recipients are prepared for surgerywith the creation of skin incisions in step 306. The method continues at307 with attachment of reference guides and performing registration. Forexample, a first cranial reference unit can be attached to a donorskeleton, a first fragment reference unit can also be attached to thedonor skeleton at a location that is different that of the first cranialreference unit. The locations of the first cranial reference unit andthe first fragment reference unit can be tracked with a first tracker.3D reconstructions of the donor skeleton can be constructed showing afirst virtual cranial reference unit and first virtual fragmentreference unit superimposed on the first 3D reconstruction at locationsthat correspond to relative positions of the first cranial referenceunit and the first fragment reference unit.

A second cranial reference unit can be attached to a recipient skeleton.A second location of the second cranial reference unit can be trackedwith a second tracker. A second 3D reconstruction of the recipientskeleton can be created with a second virtual cranial reference unitsuperimposed on the second 3D reconstruction at a location thatcorresponds to a location of the second cranial reference unit. At 308,vessels and nerves are dissected and exposed. At this stage, navigationof the patient-specific cutting guides can occur, with plan revision andupdates provided periodically. For example, a first cutting guide, suchas a patient-specific cutting guide according to the descriptionsprovided above, can be attached onto the donor skeleton at a preselectedlocation such as that corresponding to a planned cut-plane. The locationof the first cutting guide can be tracked with the first tracker. Afirst virtual cutting guide can be superimposed on the first 3Dreconstruction at a location that corresponds to a location of the firstcutting guide relative to the location of the first cranial referenceunit or the location of the first fragment reference unit.

A first virtual fragment can be formed by segmenting the 3Dreconstruction of the donor skeleton at a location adjacent to the firstvirtual cutting guide. The first virtual fragment can be superimposed onthe second 3D reconstruction of the recipient skeleton.

At step 310, a surgeon can perform an osteotomy on the donor skeleton toremove the first fragment but cutting the skeleton along a cutting pathdefined by the first cutting guide. Upon transferring the removedskeletal fragment from the donor, the first cutting guide can betracked, by the second tracker, for example, when the fragment isbrought near the recipient for attachment. The surgeon can then navigateplacement of the cutting guide as it is dynamically tracked at step 311,and will receive feedback from the system such as by referring to afirst virtual fragment that is superimposed on the second 3Dreconstruction to form a hybrid 3D reconstruction. At step 312, thefirst fragment can then be attached to the recipient skeleton via knownsurgical methods and the incisions can be sutured in step 314.

The step of superimposing the first virtual fragment on the second 3Dreconstruction of the recipient skeleton can include performing anautomated cephalometric computation for the hybrid reconstruction. Infact, the step of superimposing the first virtual fragment on the second3D reconstruction can include providing a communications link between afirst workstation on which the first 3D reconstruction is displayed anda second workstation on which the second 3D reconstruction is displayed,and initiating a data transfer protocol that causes the firstworkstation and the second workstation to send electronic signalsthrough the communications link.

Surgical methods of the embodiments described above can also includeattaching a second cutting guide at a preselected location on therecipient skeleton. The second cutting guide can also include featuresof the cutting guide described above.

For the surgical methods of embodiments described herein the donorskeleton can include a male skeleton or a female skeleton and therecipient skeleton can include a female skeleton. Alternatively, thedonor skeleton can include a male or female skeleton and the recipientskeleton can include a male skeleton.

Surgical methods of the embodiments can further include steps forassessing a size-mismatch between the donor skeleton and the recipientskeleton by measuring a dorsal maxillary interface between the firstfragment and recipient skeleton. In an embodiment, the surgical methodcan include selecting a location of the first fragment onto therecipient skeleton that minimizes dorsal step-off deformity at the areaof osteosynthesis. In an embodiment, the first cutting guide, the secondcutting guide, or both the first cutting guide and the second guide maybe or include concentric cutting guides.

Surgical methods of embodiments can further include mapping the vascularsystem on the facial anatomy of both the recipient and the donor andsuperimposing corresponding virtual representations of the vascularsystem and the facial anatomy onto the first 3D representation, such asshown in FIG. 4B

Surgical methods of embodiments can include a method for registration ofa preoperative model, for example a model reconstructed from CT data, todonor and recipient anatomy. Such a method can include: creating aplurality of indentations on the donor skeleton, creating a plurality ofvirtual markers on the first 3D reconstruction of the donor skeletoncorresponding to the locations of the indentations on the donorskeleton, placing a trackable object on at least one of the plurality ofindentations, and determining whether a subsequent location of thevirtual markers is within a predetermined tolerance relative to anactual subsequent location of the indentations.

Examples Example 1

Live transplant surgeries (n=2) between four size-mismatched swineinvestigated whether or not an embodiment could actually assist asurgical team in planning and executing a desired surgical plan. Asshown in FIGS. 9A-9B, the first live surgery confirmed the proposedutility of overcoming soft and hard tissue discrepancies related tofunction and aesthetics. The final occlusal plane within the firstrecipient was ideal and consistent with the virtual plan as seen onlateral cephalogram as shown in FIG. 10C. Pre-operative functionalpredictions of donor-to-recipient occlusion were realized based oncephalometric analyses as shown in FIG. 9C performed both before andafter surgery. Soft tissue inconsistencies of the larger-to-smallerswine scenario were also reduced following the predicted movements offace, jaw and teeth as shown in FIG. 10D.

The second live surgery showed improved success as compared to itspredecessor due to surgeon familiarity and technology modifications.System improvements and growing comfort of the surgeons led to reducedoperative times for both donor and recipient surgeries. Overall thesurgical time reduced from over 14 hours to less than 8 hours due toimproved surgical workflow and increased comfort with a system of anembodiment.

Based on the results obtained in the live and plastic bone surgeries,the functions associated with setting up a system of an embodiment(attaching references, performing registration, attaching cuttingguides) adds about 11 minutes to the total length of surgery.

The system also recorded information, such as rendering informationwhich can be stored in a storage medium of a workstation, relating thedonor fragment 1002 to the recipient 1010 qualitatively as shown bycolor mismatch 1004, which matched the post-operative CT data as shownin FIG. 10. The recipient cutting guide 1107′ was not placed as planned1107 due to an unexpected collision between the cranial reference mountand the recipient cutting guide as shown in FIGS. 11A-11B. In this case,there was anterior translation of the cutting guide (toward the tip ofthe swine's snout) by approximately 4 cm.

Overall, the donor 1106 and recipient craniums (n=4) 1108 wereregistered successfully to the reference bodies for both live surgeries.The model to patient registration error across the surgeries was 0.6(+/−0.24) mm. The cutting guide designs of the embodiments proved highlyuseful in carrying out the planned bone cuts, which compensated forsize-mismatch discrepancies between donor and recipient. Marking spheresfixated to the guides allowed real-time movement tracking and “on-table”alloflap superimposition onto the recipient thereby allowingvisualization of the final transplant result.

Example 2

Female and male donor heads (n=2), double-jaw, Le Fort III-basedalloflaps were harvested using handheld osteotomes, a reciprocating saw,and a fine vibrating reciprocating saw. Both osteocutaneous alloflapswere harvested using a double-jaw, Le Fort III-based design (acraniomaxillofacial disjunction), with preservation of the pterygoidplates, incorporating all of the midfacial skeleton, complete anteriormandible with dentition, and overlying soft tissue components necessaryfor ideal reconstruction.

Prior to transplantation, both scenarios were completed virtually giventhe gender-specific challenges to allow custom guide fabrication asshown in panels A-H of FIG. 12. Once assimilated, the donor orthognathictwo-jaw units were placed into external maxilla-mandibular fixation(MMF) using screw-fixated cutting guides to retain occlusalrelationships during the mock transplants as shown in panels A-D of FIG.13.

As shown in FIGS. 13, 14A-14B, an embodiment of a cutting guide 1307 caninclude a frame 1307′ with at least one attachment surface 1319, forexample 1 to 6 attachment surfaces, configured for attaching the cuttingguide to a skeletal feature. The cutting guide can include a navigationsurface 1317 (not shown in FIG. 13) connected to the frame. Thenavigation surface can include a reference geometry that can be trackedby a tracker, for example, via IR optical tracking. The at least oneattachment surface 1319 can include a contoured surface corresponding tocontours of portions of the skeletal feature, for example, such as thecontours of a skeletal feature that intersect a planned-cut plane asindicated by 1319′ in FIG. 12. The at least one attachment surface 1319can be detachably connected to a skeletal feature. The at least oneattachment surface 1319 can be detachably connected to an attachmentguide 1341. The attachment guide 1341 can be detachably connected to aportion of the frame 1307′. For example, attachment guides 1341 can bedetachably connected via slots integrated into frame 1307′, or held inplace against frame 1307 with screws or the like. In another embodiment,attachment guides 1341 are formed as portions of frame 1307′ but can beremoved. The frame can have a ring-like shape (as shown in FIG. 13) orcan have a cylinder-like shape (as shown in FIG. 14A). Frame 1307′having a cylinder like shape can have a bottom surface 1307″ that restsagainst a patient's soft tissue to provide support for the frame.

For example, during a surgical procedure, 3D reconstructions of portionsof a donor skeleton are created. Planned cutting planes are selected anda cutting guide with attachment surfaces having a contoured surfacecorresponding to contours of portions of the skeletal feature, forexample, such as the contours of a skeletal feature that intersect aplanned-cut plane, is designed. The designed cutting guide ismanufactured via, for example, an additive manufacturing process. Thedesigned cutting guide with an integrated navigation surface is attachedto the patient. For example, the cutting guide can be designed such thatit has a snap-on fit over the skeletal feature, which can be furthersecured to the skeletal feature with set screws. A surgeon removes adonor skeletal fragment with the cutting guide attached to the fragment.The donor skeletal fragment is then attached to the recipient. As thedonor skeletal fragment is attached to the recipient, the attachmentsurfaces are removed from the donor fragment. For example, each of theattachment guides 1341 with a corresponding attachment surface 1319 canbe detached from the frame 1307′. As this occurs, a cylindrical shapedframe 1307′ has a bottom surface 1307″ that rests against the softtissue of the patient to provide stability for the remaining portions ofthe cutting guide and to hold the navigation surface 1317′ in place.

While the invention has been illustrated respect to one or moreimplementations, alterations and/or modifications can be made to theillustrated examples without departing from the spirit and scope of theappended claims. In addition, while a particular feature of theinvention may have been disclosed with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular function. For example, the embodimentsdescribed herein can be used for navigation and modeling for osteotomyguidance during double-jaw face transplantation, single-jawmaxillofacial transplantation, and any other neurosurgical, ENT/head andneck surgery, or oral maxillofacial surgical procedure alike.

Embodiments described herein can include platforms for preoperativeplanning and intraoperative predictions related to softtissue-skeletal-dental alignment with real-time tracking of cuttingguides for two mismatched jaws of varying width, height and projection.Additional safeguards, such as collection of confidence points, furtherenable intraoperative verification of the system accuracy. This, inaddition to performing real-time plan verification via tracking anddynamic cephalometry, can considerably increase the robustness of thesystems described herein. Moreover, systems of embodiments can include amodular system that allows additional functionality to be continuallyadded.

Embodiments described herein can include an approach for resolvingconflicts in case of position discrepancies between the placement of theguide and the guide position prompted by the navigation software. Suchdiscrepancy may be due to either the guide (soft tissue interference,iatrogenic malpositioning, changes since the CT data was obtained orimperfections in cutting guide construction/printing), and/or thenavigation system (e.g. registration error, or unintended movement ofthe kinematic markers). To resolve these source(s) of discrepancy, fourindentations can be created on a bone fragment (confidence points) wherea reference kinematic marker is attached. At any time during anoperation, a surgeon can use a digitizer and compare the consistency ofthe reported coordinates of the indentations via navigation to theircoordinates with respect to a virtual computer model.

Embodiments described herein can include a system that providesreal-time dynamic cephalometrics and/or biomechanical simulation forboth planning and intraoperative guidance to ensure ideal outcomes incraniomaxillofacial surgery.

ADDITIONAL EMBODIMENTS Osseointegrated Dental Implants

Patients with poor or missing dentitions may require dental implants toimprove mastication. A popular modality with increasing indicationsincludes “osseointegrated dental implants”. Osseointegrated dentalimplants can include, and may consist of, a two-piece permanent implantdevice, which is placed into either the maxilla or mandible skeletonwith a power drill for placement and stability. A second piece, in theshape of a tooth is screwed onto the secure base. An embodiment of theCAPE system described above can be used to provide the dentist orsurgeon real-time cephalometric feedback in an effort to restore idealocclusion and predict optimized mastication with biomechanicalpredictions—as similar to maxillofacial transplantation. As such, thedentist or surgeon placing these items needs to know the bone stockquality of the jaw(s) and angle to place the framework.

Osseointegrated Craniofacial Implants and Prosthetics

Patients with severe cranial or facial disfigurement may benefit fromcustom implant reconstruction or be poor surgical candidates due tooverwhelming co-morbidities and/or because of an accompanying poorprognosis. Therefore, to help return these patients into society, someuse craniofacial implants or prosthetics as a way to restore “normalcy”.Application of these three-dimensional implants and prostheticsreplacing absent craniofacial features (i.e., skeletal, nose, eye, etc)may either be hand-molded/painted by an anaplastologist or printed with3D technology by a craniofacial technician. Either way, in anembodiment, the CAPE system described above can provide a one-stopsolution for patients requiring alloplastic and/or bioengineeredprosthetic reconstruction for large craniomaxillofacial deformities. Thecraniofacial implants can be tracked as similar to a donorface-jaw-teeth segment described above. For example, pre-placementimages of the implant or prosthetic onlay may be fabricated, andsurgical plans may be optimized since these appliances are placed withosseointegrated devices as similar to dental implants describedabove—with rigid plates and screws. As such, the surgeon placing themneeds to know the exact location, underlying bone stock quality, andangle to place the framework, and desires unprecedented visual feedbackas to the ideal position in three-dimensional space.

Craniomaxillofacial Trauma Reconstruction

Patients suffering from acute or chronic facial disfigurement are oftenseen by a craniomaxillofacial surgeon. Both penetrating and/or blunttrauma may cause significant damage to the underlying facial skeleton.As such, in an embodiment, the CAPE system technology described hereinallows the surgeon to assess and optimize bone fragment reduction andreconstruction with real-time feedback. In addition, fractures affectingthe jaws can be aided by real-time cephalometrics in hopes to restorethe patient back to their pre-trauma angle/measurements (as a way toassure proper occlusion). Navigation, as described above in anembodiment of the CAPE system, can be exceptionally helpful for orbitfractures around the eye or cranial fractures around the brain, sincethe nerve anatomy is delicate and consistent—which makes it applicableto the CAPE system. In summary, a surgeon (including the likes of aPlastic surgeon, ENT surgeon, oral/OMFS surgeon, oculoplastic surgeon,neurosurgeon) reducing craniofacial fractures needs to know the bonestock quality remaining, where plates/screws are best placed, and theoptimal plan prior to entering the operating room.

Neurosurgical Procedures

Neurosurgeons frequently perform delicate craniotomies for access forbrain surgery. Currently, there are several navigational systemsavailable. However, none of the conventional systems include featuresdescribed in the embodiments of the CAPE platform as described above.That is, the conventional systems lack the ability to assist bothpre-operatively with planning AND with intra-operative navigation forexecution assistance. In addition, the current neurosurgery systemsrequire the head to be placed in antiquated “bilateral skull clamp pins”during the entire surgery. This means that before each neurosurgeryprocedure starts, a big 3-piece clamp is crunched onto the skull of thepatient to make sure the head does not move during surgery, particularlyto allow for use of the conventional navigation systems. However,embodiments of the CAPE system, such as those described above, use asmall, modified rigid cranial reference mount which removes the need forusing a big, bulky clamp from the field and allows the surgeon to rotatethe patient's head if and when needed. To a craniofacial plasticsurgeon, who often is consulted to assist with simultaneous scalpreconstruction, elimination/removal of such pins from the surgical fieldis a huge advantage. For example, elimination of the pins makes scalpreconstruction in the setting of neurosurgery much safer since the pinsaren't present to hold back mobilization and dissection of the nearbyscalp, which is needed often for complex closure. It also, reduces therisk of surgical contamination since the current setup with pins isbulky and makes surgical draping and sterility much more difficult andawkward. A small cranial mount as part of the CAPE system is a hugeadvancement for the field.

Congenital Deformity Correction

Unfortunately, newborns are commonly born with craniofacial deformitiesto either maternal exposure or genetic abnormalities. As such, they mayhave major development problems with their skeleton and the overlyingstructures (eyes, ears, nose) may therefore appear abnormal. Inaddition, newborns may suffer from craniosynostosis (premature fusing oftheir cranial sutures) which causes major shifts in the shape of theirhead at birth. In an embodiment, the CAPE system described above, can beutilized to address such congenital deformities, irrespective ofetiology. For example, if a 16 year old needs to have major Le Fortsurgery to move the central facial skeleton into better position forwardto improve breathing, mastication, and appearance, use of the CAPEsystem technology for both pre- and intra-operatively provides a hugeadvancement for the field.

Head/Neck and Facial Reconstruction (ENT Surgery)

Head and neck surgeons in the specialty of Otolarygology (ENT) arefrequently reconstructing facial skeletons. Reasons include post-tumorresection, facial trauma, aesthetic improvement, congenital causesand/or functional improvement (nose, mouth, eyes, etc). Therefore, thisspecialty would greatly benefit from use of the CAPE system technologydescribed herein. For example, in an embodiment, use of the CAPE systemcan be used in a wide range of surgeries including such instances aspost-trauma fracture reduction/fixation, free tissue transfer planningand execution (i.e., free flap reconstruction with microsurgical fibulaflaps for large bone defects where the leg bone receives dental implantsfor jaw reconstruction), smaller jaw reconstruction cases with implantmaterials, and/or anterior skull base reconstructions with neurosurgeryfollowing tumor resection. This specialty is very diverse, and thereforethe CAPE system's easy adaptability can help make it greatly valuable tothis group of surgeons.

Computer-Assisted Cranioplasty

At least some embodiments described herein can be used for the immediatesurgical repair of large cranial defects (>5 cm²). For example,embodiments described herein may be used for designing, forming andimplanting customized craniofacial implants following benign/malignantskull neoplasm (tumor) resection (i.e. referred to as “single-stageimplant cranioplasty”). Currently, it is challenging to reconstruct suchpatients with pre-fabricated implants using conventional methods sincethe actual size/shape of the defect site is unknown until the tumor isremoved. Accordingly, use of a computer-assisted surgical system of anembodiment may significantly reduce the intraoperative time used forreshaping/resizing the customized implant. For example, embodimentsprovide visualization related to the tumor, the resulting skull defect,and the reshaped implant for exact positioning. In other words, in anembodiment, a Computer-Assisted Planning and Execution (CAPE) systemthat can be utilized for Le Fort-based, Face-Jaw-Teeth transplantationmay also be used for improving both the pre-operative planning andintra-operative execution of single-stage implant cranioplasties.Cranioplasties may be performed to reconstruct large defects followingstroke, trauma, aneurysmal bleeding, bone flap removal for infection,and oncological ablation. However, oncological defects are commonlyreconstructed with “off-the-shelf” materials, as opposed to using apre-fabricated customized implant—simply because the exact defectsize/shape is unknown. With this in mind, embodiments described hereininclude a computer-assisted algorithm that may allow surgeons toreconstruct tumor defects with pre-customized cranial implants (CCIs)for an ideal result.

Nearly 250,000 primary brain tumors/skull-based neoplasms are diagnosedeach year resulting in a range of 4500-5000 second-stage implantcranioplasties/year. Unfortunately, the common tumor defect cranioplastyis reconstructed with on-table manipulation of titanium mesh, liquidpolymethylmethacrylate (PMMA), liquid hydroxyapatitie/bone cement (HA)or autologous split-thickness calvarial bone grafts (ref), which forcesthe surgeon to shape/mold these materials to an approximate size/shape.Expectingly, this results in some form of craniofacial asymmetry and apost-operative appearance which is suboptimal. Furthermore, thedifficult shaping process may take several hours—which in turn increasesanesthesia, total blood loss, risk for infection, morbidity, and allcosts associated with longer operative times. Therefore, there issignificant opportunity to extend this CAPE to thousands of patients.

In 2002, the advent of computer-aided design and manufacturing (CAD/CAM)was used for the first time to pre-emptively match the contralateral,non-operated skull for ideal contour and appearance, which provided forthe use of CCIs. However, cranioplasties with such CCIs can only beperformed as “second stage” operations during which a clinician, such asa surgeon, ensures that the CCI fits perfectly into the skull defect.Recent developments have demonstrated the feasibility of CCIs for“single-stage cranioplasty”, but this involves using a handheld bur toshave down the pre-fabricated implant artistically. However, challengesin both assessing and predicting each tumor-resection deformitypre-surgery still limits the applicability of CCIs in this patientpopulation. For example, challenges such as 1) unknown exact tumor size,2) unknown growth from time of pre-op CT scan-to-actual day of surgery,and 3) the unknown resection margins needed to minimize localrecurrence. For these cases, the CCI would need to be reshaped/resizedintraoperatively from a size slightly larger than expected—which is aprocess that may take several (2-4) hours. However, there are noestablished planning and execution systems available to assist thesesingle-stage reconstructions. Accordingly, embodiments described hereinmay be used by surgeons in performing single-stage cranioplastyfollowing oncological resection. In other words, embodiments includealgorithms for real-time updates related to single-stage customizedimplant cranioplasty. For example, in an embodiment, there is aComputer-Assisted Planning and Execution (CAPE) system, which is aSINGLE, seamless platform capable of being used for both planning(pre-op use) and navigation (intra-op use) which overcomes thelimitations of conventional systems that do either one or the other. Inaddition, embodiments include novel hardware such as trackable cuttingguides and rigid cranial reference mount.

Orthognathic Surgery

Orthognathic surgery describes any of surgical procedure type moving thejaw and/or jaw-teeth segments. This is most commonly performed by eitheroral surgeons, oral-maxillofacial surgeons (OMFS), or plastic surgeons.It is done currently both in the hospital as an insurance case or in theoutpatient setting for a fee-for-service. It may be indicated forenhanced mastication, improved aesthetics, and/or both reasons. Havingthe ability to plan and predict jaw movements based on biomechanicalmuscle (i.e., external) forces will be immensely valuable to this field.In an embodiment, surgeons can utilize the CAPE system described aboveto predict functional jaw movements both at time of surgery and aftersurgery (1, 5, 10, 20 years post-op). In addition, in an embodiment, asurgeon can utilize the CAPE system to provide real-time cephalometricfeedback, which provides an advancement not seen in the conventionalsystems. In comparison, for the last several centuries, oral surgeonshave used splints fabricated in the dental lab pre-operatively forassistance in the operating room to help confirm dental alignment asplanned. This takes time (e.g., 4-6 hours to make by hand), effort, andmoney. In contrast to the conventional systems, surgeons utilizing theCAPE system can go to the operating room with pre-fabricated cuttingguides and tracking instruments, cut the jaws where planned, and thenmatch the teeth on the table based on real-time cephalometric feedbackand biomechanical jaw simulation to predict post-operativemastication—unlike ever before. For example, use of the CAPE system willallow surgeons to know instantaneously if the aesthetic and functionalangles/measurements are ideal and where they should be. In addition, theCAPE system is able to supply palatal cutting guides and pre-bent metalfixation plates (as opposed to the conventional methods that requirehand bending each plate for proper shape). In summary, the CAPE systemwill be a “game-changer” for orthognathic surgery.

Orthognathic Biomechanical Simulation

Many types of surgery may benefit from intra-operative biomechanicalsimulation as described here following surgical intervention, includingthose fields of craniomaxillofacial surgery and orthopedic surgery—whereboth specialties transpose bones and structural tissues to new positionsduring surgery. Complex craniomaxillofacial surgery, particularlyface-jaw-teeth transplantation or implantation of custom implants,includes replacing damaged portions of a recipient's face and underlyingskeleton with either hard and soft tissues from the patient himself orherself or a cadaveric donor (transplantation), an osseointegrativeimplant (implantation), or a tissue engineered construct. Such surgerieshave yielded sub-optimal results and a need for subsequent revisionsurgery due to patient mastication problems. For example, thepost-surgical relationship between upper and lower jaws may be differentthan that of the healthy recipient. The new occlusal plane angle,dento-facial relationships, and muscle insertions directly affect theway muscles are recruited for providing forces and motions for chewingor biting. Such positioning parameters are difficult to determine beforeor during surgery.

Embodiments thus provide computer-assisted modeling and functionalprediction for use before or during surgical intervention. Surgeriesperformed in concert with some embodiments may include one or both ofpre-operative planning and intra-operative assessment. Such planningand/or assessment may include determining changes related to masticatorymuscles affecting lower and/or upper jaws. In particular, someembodiments utilize patient-specific models, which can provide forsurgical pre-operative planning and intra-operative assessment with thesalient features of the outcome in mind. A variety of differentpositioning parameters that may be considered to obtain a positiveoutcome for this type of surgery, including muscle insertion locationsand size matching between recipient skeletal features and theimplant/transplant. More generally, embodiments may be used to assessand improve aesthetics, cephalometric measures in relation toimplant/donor-to-recipient discrepancies, and optimum teeth occlusion.Note that the term “donor” as used herein may refer to a donor separatefrom the patient, e.g., a cadaveric donor, or to the patient himself orherself when the skeletal fragment transplant is taken from the patienthimself or herself.

FIGS. 15A and 15B illustrate a biomechanical simulation of masticationin a patient skull according to some embodiments. That is, FIGS. 15A and15B depict time slices, e.g., frames, from an animated masticationsimulation. The simulation depicted in FIGS. 15A and 15B may begenerated by, or by using, an embodiment. More particularly, anembodiment may accept patient-specific data and model mastication of apatient. The modeled mastication may be displayed on a computer monitor,for example. Suitable software for executing the simulation includes,e.g., THE ANYBODY MODELING SYSTEM, available from AnyBody TechnologyA/S, of Aalborg Øst, Denmark. FIGS. 15A and 15B depict still images froma displayed example mastication simulation. The simulation of FIGS. 15Aand 15B may be used to obtain a baseline mastication simulation for apatient. The baseline mastication simulation may be compared to thesimulation shown and described in reference to FIGS. 16A and 16B. Insome embodiments, the baseline simulation is omitted.

Thus, FIGS. 15A and 15B depict three-dimensional computer-readablerepresentations of maxilla 1502, mandible 1504, and coordinate axes1506, 1508 associated therewith. The data used to represent maxilla 1502and mandible 1504 may be obtained using a computed tomography (CT) scan,e.g., a cone beam computed tomography scan, or a magnetic resonanceimaging scan, for example. The data may be stored in electronicpersistent memory. As depicted in FIGS. 15A and 15B, maxilla 1502 isassociated with coordinate axis 1506, and mandible 1504 is associatedwith coordinate axis 1508. Each axis 1504, 1506 is virtually attached toits respective three-dimensional representation and used to provideprecise virtual positioning.

Also depicted in FIGS. 15A and 15B are virtual muscles 1510 and theirrespective insertion locations 1512. Generally, virtual muscles 1510 maybe modeled as Hill-type actuators. Each virtual muscle 1510 may bemodeled using estimated optimum fiber length and estimated force atoptimum fiber length, for example. Fiber/tendon ratios may be estimated,with a portion of the total muscle length at jaw close consideredoptimum fiber length and the remaining portion as slack tendon length.At a portion of tension (e.g., 5%), each muscle's tendon may beconsidered to provide a passive force equal to the maximum isometricfiber force. In the recipient simulation of FIG. 15A, attachment sitesof virtual muscles 1510 may be determined based on imaging techniquesand/or anatomical landmarks. Alternately, or in addition, inversedynamic human masticatory biomechanics solvers, discussed immediatelybelow, may provide optimized muscle insertion locations.

In general, inverse dynamic human masticatory biomechanics may be usedto gather virtual muscle parameters. For such inverse problems,mandibular motion and temporomandibular joint reaction forces may bemeasured or otherwise empirically determined, and muscle activations orforces may be derived, e.g., estimated, therefrom. Variouscompute-implemented solvers may be utilized to that end. For example,two groups of suitable such solvers include forward dynamics-assistedand static optimizers. In the former, a set of initial muscleactivations may be used for solving the forward dynamics problem and theresulting motion and/or external forces may be compared with thereference data. An optimizer may then adjust the muscle patterns so thatthe error is minimized. In the latter, at each simulation time step, anoptimization problem may be solved that, based on muscle efforts,minimizes a (physiologically-related) function. Condylar joint load ormuscle fatigue are among the possible such objective functions. Thisapproach is computationally inexpensive and can be used for varioussensitivity analyses including optimizing muscle attachment sites.Another possible technique of optimization in masticatory dynamics isthe method of dynamic geometric optimization, where muscles arevirtually activated based on their lines of action with respect to aspecific tracked target point on a mandible.

As shown in FIG. 15A, the simulation provides an open-jawrepresentation. Activating virtual muscles 1510 causes the jaw to closeas depicted in FIG. 15B, thus simulating mastication. The simulatedmastication of FIGS. 15A and 15B may be compared to the simulatedmastication of FIGS. 16A and 16B, toward assessing whether proposedpre-surgical position parameters, or in-use intra-surgery positioningparameters, are likely to provide an acceptable outcome.

FIGS. 16A and 16B illustrate a biomechanical simulation of masticationof a hybrid craniomsaxillofacial skeleton according to some embodiments.In particular, FIGS. 16A and 16B are still images (e.g., time slices orframes) from an animated hybrid skull mastication simulation. Ingeneral, the hybrid may include a recipient portion of a mandible and/ora maxilla, as well as a portion of a donor or implant mandible ormaxilla. Without loss of generality, FIGS. 16A and 16B depict arecipient mandible 1604, and a donor or implant maxilla 1606. Thesimulation shown and discussed in reference to FIGS. 16A and 16B may beused to assess whether an acceptable outcome is likely with thesimulated set of positioning parameters.

The simulation of FIGS. 16A and 16B may be used to evaluate positioningparameters for suitability in producing an acceptable outcome.Positioning parameters suitable for evaluation using the simulationinclude fragment relative positioning and muscle insertion locations.Toward assessing whether the simulation represents an acceptableoutcome, the physician may assess whether the simulation includesadequate teeth alignment, whether the fragments are suitably matched interms of size, whether the muscle attachment sites should be adjusted,whether the fragment sizes match (between recipient and donor/implant),whether the teeth occlusion is acceptable, whether the aesthetics areacceptable, etc. A physician may view a display of the animatedsimulation and assess whether the positioning parameters of thesimulation would be suitable in the patient. Such a physician may viewthe simulated surgery and its affect on function before surgery forpreoperative planning purposes. Alternately, or in addition, thephysician my view the simulation predictions during surgery followingsurgical manipulation in order to reassess initial positioning parameterchoices or assess revised positioning parameters, for example. Aphysician may conclude, using the simulation, that one or more suchparameters should be adjusted. The physician may repeat the simulationwith the adjusted parameters, and use related information provided bythe CAPE system.

Thus, FIGS. 16A and 16B depict computer-displayed representations ofmaxilla 1602, mandible 1604, and coordinate axes 1606, 1608 associatedtherewith. The data used to represent maxilla 1602 and mandible 1604 maybe obtained using a computed tomography (CT) scan, e.g., a cone beamcomputed tomography scan, or a magnetic resonance imaging scan, forexample, and stored in persistent electronic memory. Maxilla 1602 isassociated with coordinate axis 1606, and mandible 1604 is associatedwith coordinate axis 1608. Each axis 1604, 1606, is virtually attachedto its respective three-dimensional representation and used to provideprecise positioning. Axes 1604, 1606 may be hidden in some embodiments.

Also depicted in FIGS. 16A and 16B are virtual muscles 1610 and theirrespective insertion locations 1612. As discussed above in reference toFIGS. 15A and 15B, virtual muscles 1610 may be modeled as Hill-typeactuators, with muscle parameters obtained by, for example, estimationusing inverse dynamic human masticatory biomechanics as computed bycomputer-implemented solvers. Muscle parameters include, for example,estimated optimum fiber length, estimated force at optimum fiber length,and fiber/tendon ratios.

An open-jaw representation is depicted in FIG. 16A, with a correspondingclosed-jaw simulation depicted in FIG. 16B. Activating virtual muscles1610 causes the jaw to close, simulating mastication. The simulatedmastication of FIGS. 16A and 16B may be used to assess whether proposedpre-surgical position parameters, or in-use intra-surgery positioningparameters, are likely to provide an acceptable outcome.

FIG. 17 is a workflow of a method according to various embodiments. Themethod of FIG. 17 may be implemented using electronic computingequipment, including, for example, a computed tomography scanner and adisplay device coupled to electronic processors configured to executethe steps of the method. The electronic processors may becommunicatively coupled to one or more electronic memory devices,persistent or otherwise, that contain instructions which, when executedby the processors, implement the method. The method shown and describedin reference to FIG. 17 may be used to produce simulations as shown anddescribed herein in reference to FIGS. 15A, 15B, 16A and 16B.

At block 1702, the method obtains a computer-readable three-dimensionalrepresentation of a recipient skeletal fragment. The recipient skeletalfragment typically includes a portion of a mandible, a maxilla, or both.The representation may be generated using, e.g., a computed tomography(CT) scan, e.g., a cone beam computed tomography scan, or a magneticresonance imaging scan, for example. The representation may be stored involatile and/or persistent electronic memory. The method may obtain therepresentation by, e.g., retrieving it from memory, by receiving it overa network, or by generating it using an imaging device as described

At block 1704, the method obtains a computer-readable three-dimensionalrepresentation of a donor skeletal fragment. This step refers to a donorskeletal fragment by way of non-limiting example; is some embodiments,an implant is used instead. Nevertheless, the present description refersto “donor skeletal fragment”, with the understanding that this may bereplaced by “implant” mutatis mutandis. The skeletal fragment typicallyincludes a portion of a mandible, a maxilla, or both. The representationmay be generated using a computed tomography (CT) scan such as a conebeam computed tomography scan, or a magnetic resonance imaging scan, forexample. The representation may be stored in volatile and/or persistentelectronic memory. The method may obtain the representation by, e.g.,retrieving it from memory, by receiving it over a network, or bygenerating it using an imaging device as described.

At block 1706, the method obtains placement data representing a positionof at least a portion of the donor skeletal fragment (respectively,implant) relative to at least a portion of the recipient skeletalfragment. The placement data may be in the form of, for example, dataprovided by a tracker as shown and discussed herein in reference to FIG.2, for example. Alternately, or in addition, the placement data may beobtained from a physician using a user interface to virtually manipulatethe representation of the donor skeletal fragment relative to therepresentation of the recipient skeletal fragment. In general, theplacement data is with respect to all or part of the skeletal fragmentsfor which representations were obtained, recognizing that one or both ofthe skeletal fragments may be modified by, e.g., reducing their size,before the positioning is attempted.

At block 1708, the method obtains muscle insertion data representing atleast one muscle insertion location on the donor skeletal fragment(respectively, implant), the recipient skeletal fragment, or both. Thedata may be made relative to cephalometric landmarks as describedherein. The data may be obtained from a physician using a user interfaceto virtually manipulate insertion locations of muscle representationsrelative to the representation of the donor skeletal fragment and therepresentation of the recipient skeletal fragment.

At block 1710, the method simulates contractions of one or a pluralityof muscles positioned according to the muscle insertion data obtained atblock 1708 in a representation of a surgical hybrid that includes atleast a portion of the donor skeletal fragment positioned according tothe placement data relative to at least a portion of the recipientskeletal fragment. Of note, this type of technology could be applicableto the entire human skeleton. The simulation may be performed asdescribed above in reference to FIGS. 15A, 15B, 16A and 16B. Inparticular, the simulation may utilize estimated muscle parameters asdescribed.

At block 1712, the method outputs a mastication representationrepresented by the simulation. That is, a result of the musclecontraction simulation is that the skeletal fragment representationsmove relative to each-other, thus simulating mastication. The output maybe in the form of an animation, e.g., an animation such as thatdescribed in reference to FIGS. 16A and 16B above. That is, in someembodiments, the outputting comprises displaying. Alternately, or inaddition, the output may be to a different process or system, e.g.,configured to assess whether the simulated hybrid would be acceptable.

The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “inconnection with,” and “connecting” refer to “in direct connection with”or “in connection with via one or more intermediate elements ormembers.” Furthermore, to the extent that the terms “including”,“includes”, “having”, “has”, “with”, or variants thereof are used ineither the detailed description and the claims, such terms are intendedto be inclusive in a manner similar to the term “comprising.” As usedherein, the phrase “at least one of” or “one or more of”, for example,A, B, and C means any of the following: either A, B, or C alone; orcombinations of two, such as A and B, B and C, and A and C; orcombinations of three A, B and C.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

The steps in the methods described herein may be implemented by runningone or more functional modules in an information-processing apparatussuch as general purpose processors or application-specific chips, suchas ASICs, FPGAs, PLDs, or other appropriate devices. These modules,combinations of these modules, and/or their combination with generalhardware are all included within the scope of protection of theinvention.

Certain embodiments can be performed as a computer program or set ofprograms. The computer programs can exist in a variety of forms bothactive and inactive. For example, the computer programs can exist ascomputer-readable media that include software program(s) comprised ofprogram instructions in source code, object code, executable code orother formats, firmware program(s), or hardware description language(HDL) files. Any of the above can be embodied on a non-transitorycomputer readable medium, which includes storage devices, in compressedor uncompressed form. Exemplary computer readable storage devicesinclude conventional computer system RAM (random access memory), ROM(read-only memory), EPROM (erasable, programmable ROM), EEPROM(electrically erasable, programmable ROM), and magnetic or optical disksor tapes.

What is claimed is:
 1. A method of simulating mastication, the methodcomprising: obtaining a computer-readable three-dimensionalrepresentation of a first skeletal fragment comprising a portion of atleast one of a mandible and a maxilla; obtaining a computer readablethree-dimensional representation of a recipient skeletal fragmentcomprising a portion of at least one of a mandible and a maxilla;obtaining placement data representing a position of at least a portionof the first skeletal fragment relative to at least a portion of therecipient skeletal fragment; obtaining muscle insertion datarepresenting at least one muscle insertion location on at least one ofthe first skeletal fragment and the recipient skeletal fragment;simulating a contraction of a muscle positioned according to the muscleinsertion data in a representation of a surgical hybrid comprising atleast a portion of the first skeletal fragment positioned according tothe placement data relative to at least a portion of the recipientskeletal fragment; and outputting a representation of masticationrepresented by the simulating.
 2. The method of claim 1, wherein theobtaining placement data comprises obtaining placement data prior to asurgery to transplant at least a portion of the first skeletal fragmentinto a recipient.
 3. The method of claim 1, wherein the obtainingplacement data comprises obtaining placement data during a surgery totransplant at least a portion of the first skeletal fragment into arecipient.
 4. The method of claim 3, wherein the obtaining placementdata comprises tracking a position of at least a portion of the firstskeletal fragment during the surgery.
 5. The method of claim 1, furthercomprising obtaining muscle activation data representing at least onemuscle contraction, wherein the simulating comprises simulating acontraction of a muscle according to the muscle activation data.
 6. Amethod of simulating mastication, the method comprising: obtaining acomputer-readable three-dimensional representation of anosseointegrative implant comprising a portion of at least one of amandible and a maxilla; obtaining a computer readable three-dimensionalrepresentation of a recipient skeletal fragment comprising a portion ofat least one of a mandible and a maxilla; obtaining placement datarepresenting a position of at least a portion of the osseointegrativeimplant relative to at least a portion of the recipient skeletalfragment; obtaining muscle insertion data representing at least onemuscle insertion location on at least one of the osseointegrativeimplant and the recipient skeletal fragment; simulating a contraction ofa muscle positioned according to the muscle insertion data in arepresentation of a surgical hybrid comprising at least a portion of theosseointegrative implant positioned according to the placement datarelative to at least a portion of the recipient skeletal fragment; andoutputting a representation of mastication represented by thesimulating.
 7. The method of claim 6, wherein the obtaining placementdata comprises obtaining placement data prior to a surgery to implant atleast a portion of the osseointegrative implant into a recipient.
 8. Themethod of claim 6, wherein the obtaining placement data comprisesobtaining placement data during a surgery to implant at least a portionof the osseointegrative implant into a recipient.
 9. The method of claim8, wherein the obtaining placement data comprises tracking a position ofat least a portion of the osseointegrative implant during the surgery.10. The method of claim 6, further comprising obtaining muscleactivation data representing at least one muscle contraction, whereinthe simulating comprises simulating a contraction of a muscle accordingto the muscle activation data.
 11. A system for simulating mastication,the system comprising at least one electronic memory and at least oneelectronic processor, the at least one electronic memory includinginstructions which, when executed by the at least one electronicprocessor, cause the at least one electronic processor to perform amethod comprising: obtaining a computer-readable three-dimensionalrepresentation of a first skeletal fragment comprising a portion of atleast one of a mandible and a maxilla; obtaining a computer readablethree-dimensional representation of a recipient skeletal fragmentcomprising a portion of at least one of a mandible and a maxilla;obtaining placement data representing a position of at least a portionof the first skeletal fragment relative to at least a portion of therecipient skeletal fragment; obtaining muscle insertion datarepresenting at least one muscle insertion location on at least one ofthe first skeletal fragment and the recipient skeletal fragment;simulating a contraction of a muscle positioned according to the muscleinsertion data in a representation of a surgical hybrid comprising atleast a portion of the first skeletal fragment positioned according tothe placement data relative to at least a portion of the recipientskeletal fragment; and outputting a representation of masticationrepresented by the simulating.
 12. The system of claim 11, wherein theobtaining placement data comprises obtaining placement data prior to asurgery to transplant at least a portion of the first skeletal fragmentinto a recipient.
 13. The system of claim 11, wherein the obtainingplacement data comprises obtaining placement data during a surgery totransplant at least a portion of the first skeletal fragment into arecipient.
 14. The system of claim 13, wherein the obtaining placementdata comprises tracking a position of at least a portion of the firstskeletal fragment during the surgery.
 15. The system of claim 11,wherein the at least one electronic memory further comprisesinstructions which, when executed by the at least one electronicprocessor, further cause the at least one electronic processor to obtainmuscle activation data representing at least one muscle contraction,wherein the simulating comprises simulating a contraction of a muscleaccording to the muscle activation data.
 16. A system for simulatingmastication, the system comprising at least one electronic memory and atleast one electronic processor, the at least one electronic memoryincluding instructions which, when executed by the at least oneelectronic processor, cause the at least one electronic processor toperform a method comprising: obtaining a computer-readablethree-dimensional representation of an osseointegrative implantcomprising a portion of at least one of a mandible and a maxilla;obtaining a computer readable three-dimensional representation of arecipient skeletal fragment comprising a portion of at least one of amandible and a maxilla; obtaining placement data representing a positionof at least a portion of the osseointegrative implant relative to atleast a portion of the recipient skeletal fragment; obtaining muscleinsertion data representing at least one muscle insertion location on atleast one of the osseointegrative implant and the recipient skeletalfragment; simulating a contraction of a muscle positioned according tothe muscle insertion data in a representation of a surgical hybridcomprising at least a portion of the osseointegrative implant positionedaccording to the placement data relative to at least a portion of therecipient skeletal fragment; and outputting a representation ofmastication represented by the simulating.
 17. The system of claim 16,wherein the obtaining placement data comprises obtaining placement dataprior to a surgery to implant at least a portion of the osseointegrativeimplant into a recipient.
 18. The system of claim 16, wherein theobtaining placement data comprises obtaining placement data during asurgery to implant at least a portion of the osseointegrative implantinto a recipient.
 19. The system of claim 18, wherein the obtainingplacement data comprises tracking a position of at least a portion ofthe osseointegrative implant during the surgery.
 20. The system of claim16, wherein the at least one electronic memory further comprisesinstructions which, when executed by the at least one electronicprocessor, further cause the at least one electronic processor to obtainmuscle activation data representing at least one muscle contraction,wherein the simulating comprises simulating a contraction of a muscleaccording to the muscle activation data.